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#1220
by
msat
on 26 Jan, 2018 14:27
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I'm under the impression that RL de-orbits the 2nd stage, so restart of the stage's Rutherford seems likely.
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#1221
by
meberbs
on 26 Jan, 2018 14:40
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* At 20:55, the ejection of the prominent battery pack can clearly be seen, but a fraction of a second later, a second pack can be seen at the top of the frame, making me think they ejected two packs at once.
First, welcome to the forum.
Symmetric placement for balance makes sense.
Does anyone know why the attitude correction looks so large?
In addition to what edzieba mentioned, the different thrust-weight ratio after staging may change the desired thrust angle depending on how they want to handle gravity losses.
* I have also been wondering about why they paint their launcher black (or leave the carbon fibre surface as is). From my experience, usually white paint is used to minimise solar irradiance. Surely they must have problems with aeroheating? At 17:28, the outside of one fairing half can be seen, and it looks positively glossy, so no apparent heat "damage". If that is just a "clear-coated" carbon fibre surface, how do they get away without using any kind of thermal protection?
Painting would add weight, so if it is not needed for protection, it makes sense to skip. Also, for any heating other than incident radiation, black is the best color to deal with it because of higher emissivity.
Aeroheating shouldn't be a major concern during launch. You don't want to fight high drag during launch, so launch trajectories try to get above as much of the atmosphere as possible as before velocity gets to a point where drag is significant. Certainly not enough to cause scorching or require thermal protection.
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#1222
by
lrk
on 26 Jan, 2018 14:47
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* I have also been wondering about why they paint their launcher black (or leave the carbon fibre surface as is). From my experience, usually white paint is used to minimise solar irradiance. Surely they must have problems with aeroheating? At 17:28, the outside of one fairing half can be seen, and it looks positively glossy, so no apparent heat "damage". If that is just a "clear-coated" carbon fibre surface, how do they get away without using any kind of thermal protection?
You
do want to have your LOX tank white to decrease boil off before launch... but there is a convenient white layer of ice that forms anyway, so apparently this isn't a major issue. Adding paint would only reduce the payload capacity.
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#1223
by
Schwarzschild
on 26 Jan, 2018 15:51
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First, welcome to the forum.
Thanks!
* I have also been wondering about why they paint their launcher black (or leave the carbon fibre surface as is). From my experience, usually white paint is used to minimise solar irradiance. Surely they must have problems with aeroheating? At 17:28, the outside of one fairing half can be seen, and it looks positively glossy, so no apparent heat "damage". If that is just a "clear-coated" carbon fibre surface, how do they get away without using any kind of thermal protection?
Painting would add weight, so if it is not needed for protection, it makes sense to skip. Also, for any heating other than incident radiation, black is the best color to deal with it because of higher emissivity.
Aeroheating shouldn't be a major concern during launch. You don't want to fight high drag during launch, so launch trajectories try to get above as much of the atmosphere as possible as before velocity gets to a point where drag is significant. Certainly not enough to cause scorching or require thermal protection.
Hmm, I am not convinced. OK, a black body is the ideal emitter and if the aeroheating is expected to be higher than the solar irradiance, it makes sense. However, I have seen bigger launchers use thermal protection on their fairings. See for example
here: In "Step 8" of the slide show you can see some light brownish thermal protection applied on the fairing. Surely this would not be done if it would not be required?
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#1224
by
Stan-1967
on 26 Jan, 2018 16:14
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Hmm, I am not convinced. OK, a black body is the ideal emitter and if the aeroheating is expected to be higher than the solar irradiance, it makes sense. However, I have seen bigger launchers use thermal protection on their fairings. See for example here: In "Step 8" of the slide show you can see some light brownish thermal protection applied on the fairing. Surely this would not be done if it would not be required?
I think the thermal management of a carbon composite tank is easier than other common tank materials, like aluminum-lithium. The thermal conductivity of Al:Li is relatively high, meaning heat can leave the system readily. Carbon fiber composite should have a thermal conductivity at least an order of magnitude less. Essentially the carbon fiber tanks are their own insulation. No need for an exterior coating. Found this link with some comparative thermal properties.
https://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html
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#1225
by
Bananas_on_Mars
on 26 Jan, 2018 17:41
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I guess there's also the case that the payloads for Electron aren't as delicate as some of the bigger payloads that have special environmental requirements.
Also, some of those payloads would sit on the pad for quite some time, while Rocketlab could always go back to horizontal and into the hangar if there's a delay.
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#1226
by
douglas100
on 26 Jan, 2018 18:02
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On the point about the thermal control of the payload, Electron doesn't seem to have aircon going to the fairing. Anyone know if this is the case?
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#1227
by
Stan-1967
on 26 Jan, 2018 19:31
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On the point about the thermal control of the payload, Electron doesn't seem to have aircon going to the fairing. Anyone know if this is the case?
Rocketlab's Electron User guide ( see page 14) says the fairing can have environmental controls, although presence of this feature seems to be payload specific.
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#1228
by
ArbitraryConstant
on 26 Jan, 2018 19:54
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I'm under the impression that RL de-orbits the 2nd stage, so restart of the stage's Rutherford seems likely.
That would make sense if they did circularization at 500 km with the second stage, but it looked like they did that with the kick stage, leaving the second stage in an elliptical orbit with 300 km perigee. That seems short lived enough that they don't strictly need deorbit.
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#1229
by
WmThomas
on 26 Jan, 2018 20:13
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Mods: Is it time to create a Rocketlab directory/section? I'm seeing multiple threads here about Rocketlab, Electron, Electron launches.
Rocketlab says it is moving into operational posture. That's another reason. Presumably, they will have a lot of launches in coming months.
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#1230
by
john smith 19
on 26 Jan, 2018 20:19
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So I have finally registered an account here 
* I have also been wondering about why they paint their launcher black (or leave the carbon fibre surface as is). From my experience, usually white paint is used to minimise solar irradiance. Surely they must have problems with aeroheating? At 17:28, the outside of one fairing half can be seen, and it looks positively glossy, so no apparent heat "damage". If that is just a "clear-coated" carbon fibre surface, how do they get away without using any kind of thermal protection?
Welcome to the forum.
Black sounds an odd choice but as others have pointed out it's as good an emitter as it is an absorber, and since one stage does not make orbit and the other does not last long that's not two big an issue. Something like it was asked about how much LOX tank insulation was needed on F9 or the old Steel tank Atlases. Aluminaum alloy is 10x as conductive as Steel, and I think CRFT is
less conductive than Steel. A layer of paint, combined with the water vapour frozen out of the air, was enough to cut boil off to an acceptable level.
[EDIT. Oops.
Turns out according to the web site listed earlier that raw carbon fiber can be 2.38x higher in thermal conductivity. However carbon fiber composite (using Epoxy resin) is 0.01x that level, which works out to be 26x lower than Aluminum alloy. IE 1/26 Aluminum. ]
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#1231
by
ArbitraryConstant
on 26 Jan, 2018 21:20
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Mods: Is it time to create a Rocketlab directory/section? I'm seeing multiple threads here about Rocketlab, Electron, Electron launches.
Rocketlab says it is moving into operational posture. That's another reason. Presumably, they will have a lot of launches in coming months.
I was actually thinking of creating a thread on the kick stage but thought it would be excessive.
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#1232
by
Robotbeat
on 27 Jan, 2018 01:47
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Mods: Is it time to create a Rocketlab directory/section? I'm seeing multiple threads here about Rocketlab, Electron, Electron launches.
Rocketlab says it is moving into operational posture. That's another reason. Presumably, they will have a lot of launches in coming months.
I was actually thinking of creating a thread on the kick stage but thought it would be excessive.
I don't think it is excessive. It's an interesting piece of hardware with some interesting history (green monoprop) and technology.
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#1233
by
gongora
on 27 Jan, 2018 02:07
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#1234
by
ringsider
on 27 Jan, 2018 06:09
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I was actually thinking of creating a thread on the kick stage but thought it would be excessive.
I think the kick stage is a very interesting development. It raises all kinds of questions about the performance of the electric cycle and the core capability of Electron's first two stages.
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#1235
by
Kabloona
on 27 Jan, 2018 14:02
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I think the kick stage is a very interesting development. It raises all kinds of questions about the performance of the electric cycle and the core capability of Electron's first two stages.
What questions? Pegasus has HAPS, which is basically the same thing.
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#1236
by
john smith 19
on 27 Jan, 2018 14:16
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I think the kick stage is a very interesting development. It raises all kinds of questions about the performance of the electric cycle and the core capability of Electron's first two stages.
What questions? Pegasus has HAPS, which is basically the same thing.
HAPS is a fairly conventional pressure fed hypergolic stage. Which means it has all the issues around handling very toxic hypergols. This stuff seems to capable of an Isp at 300secs, be a mono-propellant and have unusually mass properties, more like a solid
Which would make it quite interesting in its own right.
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#1237
by
Kabloona
on 27 Jan, 2018 15:04
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I think the kick stage is a very interesting development. It raises all kinds of questions about the performance of the electric cycle and the core capability of Electron's first two stages.
What questions? Pegasus has HAPS, which is basically the same thing.
HAPS is a fairly conventional pressure fed hypergolic stage. Which means it has all the issues around handling very toxic hypergols. This stuff seems to capable of an Isp at 300secs, be a mono-propellant and have unusually mass properties, more like a solid
Which would make it quite interesting in its own right.
Is the new monopropellant interesting? Yes.
Does a small pressure-fed monopropellant kick stage atop a small 2-stage launcher "raise all kinds of questions" about capability of the 2 stages beneath it? No more so than HAPS raises questions about the capability of the Pegasus solid stages.
(And BTW, HAPS is monoprop hydrazine, not hypergolic. But yes, still toxic.)
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#1238
by
jabe
on 27 Jan, 2018 15:08
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I was actually thinking of creating a thread on the kick stage but thought it would be excessive.
I think the kick stage is a very interesting development. It raises all kinds of questions about the performance of the electric cycle and the core capability of Electron's first two stages.
To me this acts like a little tug .. great mass saver.. "simple" solution to "restart 2nd stage" issues to circularize/trim final orbit
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#1239
by
Kabloona
on 27 Jan, 2018 15:11
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I was actually thinking of creating a thread on the kick stage but thought it would be excessive.
I think the kick stage is a very interesting development. It raises all kinds of questions about the performance of the electric cycle and the core capability of Electron's first two stages.
To me this acts like a little tug .. great mass saver.. "simple" solution to "restart 2nd stage" issues to circularize/trim final orbit
Yes, just like Pegasus HAPS. The concept is not new.
